1. Field of the Invention
Embodiments of the present invention generally relate to a method and apparatus for orientation detection of an image.
2. Description of the Related Art
Digital cameras are widely used by consumers. At normal shooting position, a consumer obtains a landscape image. However, the consumer sometimes obtains a portrait image by rotating the camera. We show an example of different image orientation in FIG. 1. The top two images have 0 degree and 180 degree orientation, also known as landscape orientation. The bottom two images have 90 degree and 270 degree orientation, also known as portrait orientation.
Images with wrong orientation (90, 180, 270 degree) should be corrected for camera users. Otherwise, camera users need to correct them manually. Also, many image processing and computer vision algorithms (e.g. content-based image retrieval, face or object detection) assume that the top of the image corresponds to the top of the scene, which is not true for images with wrong orientation. If the camera does not correct 180, 90, or 270 degree orientation, these algorithms cannot work properly. After image orientation has been detected, a computer can easily correct orientation by rotating the image.
High-end digital cameras are equipped with motion sensors that detect camera rotation. However, low-end digital cameras or camera phones cannot afford them. For those cameras, camera users perform image orientation detection and correction manually. It is challenging to detect image orientation automatically. Some image orientation algorithms have been proposed for image processing applications on desktop PC. However, they are too complex to be implemented on the digital cameras. Also, a desirable method for digital cameras should be universal, since digital cameras will be used to capture different kinds of images. It also should have low computation complexity and low memory, due to the cost and shot-to-shot constraints of digital cameras.
Therefore, there is a need for an improved method and/or apparatus for determining image orientation.